1. Field of the Invention
This invention relates to alkaline earth halide x-ray phosphors. More particularly it relates to an improved europium-activated barium fluorochloride x-ray phosphor composition.
2. Prior Art
It has been known for some time that certain alkaline earth halides luminesce under x-ray excitation. U.S. Pat. No. 2,303,963 discloses a procedure for preparing barium fluorochloride. That patent, however, does not mention any activator.
Great Britain Pat. No. 1,161,871 and 1,254,271 also disclose processes for preparing various x-ray phosphors including europium-activated barium fluorochloride. Netherlands Pat. No. 7,206,945 discloses a variety of alkaline earth halides activated by europium. The intensity of emission of many of those phosphors is superior to calcium tungstate which is the present industry standard x-ray phosphor.
There is a need for a brighter x-ray phosphor because a brighter phosphor will tend to decrease the length of time of x-ray exposure required to obtain effective resolution. Alternatively, a brighter phosphor can decrease the amount of silver halide needed in the film if the exposure is held constant. The former is a health safety advantage while the latter is an economic advantage.
It is believed, therefore, that an x-ray phosphor which is brighter than the alkaline earth halides activated by europium, such as is disclosed in the prior art, would be an advancement in the art.